1. Field of the Invention
This invention relates to an improved wood-type core-shell golf club head, and, more particularly, to a unique structure which effectively transmits and reduces absorption of shock at impact of the club head with a golf ball.
2. Description of the Relevant Art
Wood-type core-shell golf club heads are disclosed in Japanese Utility Model Publication Sho. No. 50-113559, which shows a face side of the club head made of carbon fiber reinforced plastic (FRP) cloth. Another such wood-type FRP golf club head is disclosed in Japanese Patent Publication Sho. No. 57-203461, in which the entire shell of the club head is reinforced with short carbon fibers. Anderson, in U.S. Pat. No. 3,598,693 in a molding composition, utilizes short fibers in a substantially parallel arrangement to increase hardness. Hayashi, in Great Britain Patent No. 2,115,293, provides a golf club head using only short fibers impregnated in a synthetic resin. Monget, in Great Britain Patent No. 2,103,667 teaches the incorporation of intertwined filaments to brace a thermoplastic resin tube or beam.
However, none of these references provide a homogeneous mixture of fibers of predetermined composition and length, in a selected weight ratio of each, in a wood type core-shell golf club head, to effectively transmit and reduce absorption of shock at impact. In particular, the poor uniformity of the fibers of the prior art, tend to generate fine cracks in the shell during transmission of shot impulse from the face side due to microscopic unevenness in elasticity and strength. In addition, the interspersion, diffusion and interference of elastic waves during such transmission are caused by shock absorption of resin particles which fill the spaces between the long fibers, leading to poor user feeling at impact.
Accordingly, the object of the invention is to provide an improved wood-type core-shell golf club head structure which displays enhanced strength and feeling at impact of the golf head with the golf ball.
Another object of the present invention is to provide a microscopically uniform homogeneous mixture of reinforcement fibers in a club head core-shell construction, which effectively transmits and reduces absorption of sock at impact.